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authorMikulas Patocka <mpatocka@redhat.com>2011-06-29 00:48:19 +0200
committerHelge Deller <deller@gmx.de>2016-06-04 22:05:07 +0200
commitbe24a89700eef61bedaba40f3b05ef07f5806e38 (patch)
tree818288f6657c04b9d2ec91f1572ab78c49ef7bb8
parent049ec1b5a76d34a6980cccdb7c0baeb4eed7a993 (diff)
downloadlinux-be24a89700eef61bedaba40f3b05ef07f5806e38.tar.gz
parisc: Fix backtrace on PA-RISC
This patch fixes backtrace on PA-RISC There were several problems: 1) The code that decodes instructions handles instructions that subtract from the stack pointer incorrectly. If the instruction subtracts the number X from the stack pointer the code increases the frame size by (0x100000000-X). This results in invalid accesses to memory and recursive page faults. 2) Because gcc reorders blocks, handling instructions that subtract from the frame pointer is incorrect. For example, this function int f(int a) { if (__builtin_expect(a, 1)) return a; g(); return a; } is compiled in such a way, that the code that decreases the stack pointer for the first "return a" is placed before the code for "g" call. If we recognize this decrement, we mistakenly believe that the frame size for the "g" call is zero. To fix problems 1) and 2), the patch doesn't recognize instructions that decrease the stack pointer at all. To further safeguard the unwind code against nonsense values, we don't allow frame size larger than Total_frame_size. 3) The backtrace is not locked. If stack dump races with module unload, invalid table can be accessed. This patch adds a spinlock when processing module tables. Note, that for correct backtrace, you need recent binutils. Binutils 2.18 from Debian 5 produce garbage unwind tables. Binutils 2.21 work better (it sometimes forgets function frames, but at least it doesn't generate garbage). Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Helge Deller <deller@gmx.de>
-rw-r--r--arch/parisc/kernel/unwind.c22
1 files changed, 14 insertions, 8 deletions
diff --git a/arch/parisc/kernel/unwind.c b/arch/parisc/kernel/unwind.c
index ddd988b267a9..e278a87f43cc 100644
--- a/arch/parisc/kernel/unwind.c
+++ b/arch/parisc/kernel/unwind.c
@@ -75,7 +75,10 @@ find_unwind_entry(unsigned long addr)
if (addr >= kernel_unwind_table.start &&
addr <= kernel_unwind_table.end)
e = find_unwind_entry_in_table(&kernel_unwind_table, addr);
- else
+ else {
+ unsigned long flags;
+
+ spin_lock_irqsave(&unwind_lock, flags);
list_for_each_entry(table, &unwind_tables, list) {
if (addr >= table->start &&
addr <= table->end)
@@ -86,6 +89,8 @@ find_unwind_entry(unsigned long addr)
break;
}
}
+ spin_unlock_irqrestore(&unwind_lock, flags);
+ }
return e;
}
@@ -303,18 +308,16 @@ static void unwind_frame_regs(struct unwind_frame_info *info)
insn = *(unsigned int *)npc;
- if ((insn & 0xffffc000) == 0x37de0000 ||
- (insn & 0xffe00000) == 0x6fc00000) {
+ if ((insn & 0xffffc001) == 0x37de0000 ||
+ (insn & 0xffe00001) == 0x6fc00000) {
/* ldo X(sp), sp, or stwm X,D(sp) */
- frame_size += (insn & 0x1 ? -1 << 13 : 0) |
- ((insn & 0x3fff) >> 1);
+ frame_size += (insn & 0x3fff) >> 1;
dbg("analyzing func @ %lx, insn=%08x @ "
"%lx, frame_size = %ld\n", info->ip,
insn, npc, frame_size);
- } else if ((insn & 0xffe00008) == 0x73c00008) {
+ } else if ((insn & 0xffe00009) == 0x73c00008) {
/* std,ma X,D(sp) */
- frame_size += (insn & 0x1 ? -1 << 13 : 0) |
- (((insn >> 4) & 0x3ff) << 3);
+ frame_size += ((insn >> 4) & 0x3ff) << 3;
dbg("analyzing func @ %lx, insn=%08x @ "
"%lx, frame_size = %ld\n", info->ip,
insn, npc, frame_size);
@@ -333,6 +336,9 @@ static void unwind_frame_regs(struct unwind_frame_info *info)
}
}
+ if (frame_size > e->Total_frame_size << 3)
+ frame_size = e->Total_frame_size << 3;
+
if (!unwind_special(info, e->region_start, frame_size)) {
info->prev_sp = info->sp - frame_size;
if (e->Millicode)